| 摘要 |
PURPOSE:To make the sections of differente frequency ultrasonic wave beams coincide up to a specified point or after reaching it in the direction of the sending and receiving directions by dividing a piezo electric element and making it possible to select the operation of its part or whole. CONSTITUTION:Piezo electric elements 10 and 12 have the same opening and arranged by stacking them in the direction of the sending and receiving of an ultrasonic wave. Now the element 10 is made to receive and send the ultrasonic wave of frequency f1 and the element 12 is made to receive and send the ultrasonic wave of frequency f2. Then the element 10 is divided and only its central part 10a is made to operate. The opening D1 of this operating part and the opening D2 of the element 12 are made to have the relation: D1f1=D2f2. By this relation the ultrasonic wave beam of the frequency f1 and that of the frequency f2 coincide after the frequency D22/4lambda2 (lambda2 is the wave length for the frequency f2), and, furthermore, the side lobe does not become large. Accordingly, with this arrangement the cross-section of the ultrasonic wave beams of different frequencies can be made to be the same after a specified point or up the specified point. |
